Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$228.92	5.717%	$242.0074	$242.01	$242.00	$242.00
Purchase #2	$24.53	11.796%	$27.4236	$27.42	$27.40	$27.40
Purchase #3	$150.78	6.136%	$160.0319	$160.03	$160.05	$160.00
Purchase #4	$101.44	10.751%	$112.3458	$112.35	$112.35	$112.30
Purchase #5	$189.85	3.577%	$196.6409	$196.64	$196.65	$196.60
Purchase #6	$81.64	11.595%	$91.1062	$91.11	$91.10	$91.10
Purchase #7	$130.57	10.295%	$144.0122	$144.01	$144.00	$144.00
7 purchase totals =	$907.73		$973.5680	$973.57	$973.55	$973.40